Objective To investigate the effects of flow shear stress and mass transport on the construction of largescale tissue engineered bone using a perfusion bioreactor. Methods Bone marrow (20 mL) was harvested from the il iac crestof the healthy volunteer, and then hBMSCs were isolated, cultured and identified. The hBMSCs at passage 3 were seeded on the critical-size β-TCP scaffold and cultured in a perfusion bioreactor for 28 days. Different flow shear stress (1 ×, 2 × and 3 ×) and different mass transport (3, 6 and 9 mL/min) were exerted on the cells seeded on the scaffold by changing the viscosity of media or perfusion flow rate. The cell prol iferation and ALP activity of cells seeded on the scaffold were detected, and histology observation and morphology measurement of cell/scaffold complex were conducted. Results When the perfusion flow rabe was 3 mL/min, the cell viabil ity of 2 × group was higher than that of other groups (P lt; 0.05). When the flow shear stress was 3 ×, no significant differences were found among 3, 6 and 9 mL/min in cell viabil ity (P gt; 0.05). When the perfusion flow rate was 3 mL/min, the activity of ALP of 2 × and 3 × groups was higher than that of 1 × group (P lt; 0.05). When the flow shear stress was 3 ×, the activity of ALP of 6 mL/min group was the highest (P lt; 0.05). After 28 days of perfusion culture, the ECM of all the groups distributed throughout the scaffold, and the formation and mineral ization of ECM was improved with the increase of flow shear stress when the perfusion flow rate was 3 mL/min. However, the increase of perfusion flow rate decreased the mineral ization of ECM when the flow shear stress was 3 ×. Conclusion As two important fluid dynamics parameters affecting the construction of large-scale tissue engineered bone, the flow shear stress and the mass transport should be measured duringthe process of constructing large-scale tissue engineered bone so as to maximize their roles.
Objective To investigate the effect of applying a tourniquet on perioperative blood loss and short-term effectiveness in primary total knee arthroplasty (TKA). Methods A total of 94 patients (94 knees) with osteoarthritis underwent primary TKA between September 2010 and December 2011, whose data met the inclusion criteria and were retrospectively analyzed. A tourniquet was used in 51 cases (group A), no tourniquet in 43 cases (group B). There was no significant difference in gender, age, affected side, body mass index, preoperative hemoglobin (Hb) level, range of motion (ROM), visual analogue scale (VAS), Hospital for Special Surgery (HSS) score, Western Ontario and McMaster University Osteoarthritis Index (WOMAC) between 2 groups (P gt; 0.05). The data were compared between 2 groups, including hematocrit (Hct), Hb, hidden blood loss, dominant blood loss, theoretical total blood loss, the operation time, hospitalization days, increasing rate of circumference length above 10 cm of the knee, VAS score, ROM, HSS score, and WOMAC score. Results Four cases (7.84%) of group A and 1 case (2.33%) of group B received blood transfusions, showing no significant difference (χ2=1.410, P=0.235). There was no significant difference in the Hb and Hct between 2 groups at 2 days after operation (P gt; 0.05). The dominant blood loss of group A was significantly less than that of group B (P lt; 0.05), while the hidden blood loss of group A was significantly more than that of group B (P lt; 0.05), but there was no significant difference in theoretical total blood loss between 2 groups (t=0.662, P=0.510). The operation time, hospitalization days, and VAS score at 3 days showed no significant difference between 2 groups (P gt; 0.05). The wound healed by first intention after operation without related complication. At 3 days after operation, the increasing rate of circumference length above 10 cm of the knee in group A was significantly higher than that of group B (t=9.435, P=0.000), but no significant difference at 7 days (t=0.462, P=0.645). At 3 and 5 days after operation, the ROM values in group B were significantly larger than those of group A (P lt; 0.05), but no significant difference at 7 days (t= — 1.279, P=0.204). The patients were all followed up 12-18 months (mean, 14.3 months). There was no significant difference in the HSS score between 2 groups at 1 year after operation (t=0.952, P=0.344), but significant difference was found in the WOMAC score between 2 groups (t= — 2.488, P=0.015). The X-ray films showed that the prosthesis was in good position, without loosening, subsidence, or osteolysis. Conclusion Application of a tourniquet in TKA increases hidden blood loss, and there is no obvious advantage in reducing transfusion rate compared with the non-tourniquet group, so it is recommended to reduce the time and pressure of the tourniquet for patients with high-risk of thrombosis.